A semiconductor relay device (photo relay device) is used in various machines. Specially, it is commonly used as a substitution of a mechanical relay of an IC tester. One advantage of the semiconductor relay is its easiness to insulate a measured IC and measurement. Another advantage is its long life by not having contact points. However, an improvement of the high frequency characteristics is desired, among other improvements.
As the clock frequency of the IC increases, the transmission speed of a signal to be used by the IC tester increases by several 100 MHz or several GHz, as well. Accordingly, high frequency transmission is a requirement for semiconductor relay devices.
A semiconductor relay device has a light-emitting element, a photo-detecting element and a switching circuit, as main composition parts. And, it has also a terminal and a wiring between those inside parts, and between the inside part and the outside circuit.
A conventional semiconductor relay device is described in Japanese patent laid open No. 2003-8050.
But, in a conventional semiconductor relay device, a characteristic impedance of input signal wiring and output signal wiring is beyond several 100Ω. On the other hand, a characteristic impedance of a mounting circuit board is about 50Ω. So there is a discontinuity of characteristic impedance between the input signal wiring and the mounting circuit board, and between the mounting circuit board and the output wiring. Therefore, multiplex reflection occurs in the semiconductor relay device. This multiplex reflection degrades a waveform of a high frequency, as the speed of semiconductor relay device increases.